This invention relates to heat exchangers, and more particularly to heat exchanger construction with improved core thermal fatigue life.
Thermal stresses exist in localized zones of formed plate counterflow type heat exchangers for gas turbines. The highly stressed hot areas of particular concern are those located adjacent the hot face of the heat exchanger core between the air outlet manifolds, which have high thermal lag, or inertia, and the core, which has a very low thermal inertia. Because of the existence of high temperature gradients in such areas, and throughout the core, thermal fatigue cracking is apt to occur, which can cause leakage between the hot gas and air in the core passages or with the outside of the heat exchanger. Generally, thermal stresses in the core decrease in the direction of hot gas flow since the temperature gradients decrease in that direction.
An example of prior art heat exchanger construction related to thermal fatigue life is U.S. Pat. No. 3,601,185 to Rothman. Other prior art is U.S. Pat. No. 2,462,139 to Sparkes; U.S. Pat. No. 2,952,445 to Ladd; U.S. Pat. No. 3,282,011 to Meserole et al; U.S. Pat. No. 3,540,530 to Kritzer; and U.S. Pat. No. 3,542,124 to Manfredo.